A microphone placed inside a watchcase may be used for recognising the watch user's voice. The microphone must thus be able to perform reproducible voice recording regardless of the position of the watch worn on a user's wrist. Further, the voice recording by the microphone must not depend upon the distance between the watch when worn and the user's skin, if the bracelet is tight or loose. Moreover, the possible influence of obstacles in the watch user's surroundings, i.e. furniture, walls or other objects, must be minimised as far as possible.
Acquisition of an audio signal by a watch may be influenced by reflective surfaces that generate echoes. These reflective surfaces may be, for example, a table, walls, the watch user himself, or prominent parts of the middle part of the watchcase. Signal acquisition may also be influenced by cavities that generate resonance, for example between the watchcase and the arm or between the horns of the case and the bracelet.
Another particular situation is when voice recognition is performed with the watch on a base attached to a computer. Significant reflections can be generated on the table and can alter the features of the audio signal that is recorded as the reference for future recognition when the watch is worn on the wrist. This leads to a very poor recognition rate, which is a drawback.